Electron impact coherence and polarization parameters for the excitation of the 51P state in strontium

Abstract

The electron impact excitation of the 51P state in strontium has been studied by the electron-photon coincidence technique. The Stokes parameters P1, P2, and P3, of the decay transition 51P1-51S0 at lambda =460.7 nm have been measured for an incident electron energy of 45 eV. The measurements extend over the electron scattering angles 30 degrees to 113 degrees . The polarization correlation data have been analysed to yield the electron impact coherence parameters (EICP) for the excitation of the Sr(51P) state. The results of the total polarization vector provide evidence of the coherent nature of the 51S0-51P1-51S0 excitation/de-excitation process in this relatively heavy He-like atom. The measurements provide a sensitive test for the theoretical models which involve the influence of strong electron correlation effects. Substantial agreement is found between these first measurements and the two calculations which have just become available.